In regions of the world that experience significant snowfall amounts, snow is typically cleared from streets and roads by trucks equipped with snowplows. A snowplow blade is mounted on the front of the plow truck via a mount arrangement that allows the snowplow blade to be tilted and lifted as required. In order to clear the right-hand driving lane, the snowplow blade is typically pivoted or angled to the right, so that the snow that is collected and pushed by the snowplow blade ahead of the truck is deflected and cast toward the right, to be discharged from the trailing discharge end of the snowplow blade (i.e. the right end in this case). The snow discharged from the discharge end of the snowplow blade forms a ridge or snowbank of accumulated snow along the right edge of the roadway. As the plow truck drives forward along the road, it will thus cast a continuous snowbank or ridge of snow, as long as there is snow on the road to be cleared, and the snowplow blade is lowered into the plowing position.
This continuous snowbank or ridge of discharged snow causes problems wherever side roads or driveways or the like (also simply called “intersecting roads” herein) join the road being plowed. Namely, the continuous snowbank formed by the snow discharged from the snowplow will continue without interruption across the mouth of the driveway or side road. Because it is formed by snow collected across the entire width of the snowplow blade, the resulting snowbank is generally significantly higher than the depth of the accumulated snowfall. Also, because the advancing snowplow tends to compact the snow, the resulting snowbank or ridge of discharged snow tends to be denser, harder and more solid than the accumulated snowfall. As such, the snowbank extending continuously across the mouth of the driveway or side road becomes a significant blockage and impediment to travel. Every time a snowplow passes by the mouth of the intersecting road, more snow will be added to the snowbank extending across it.
Such a snowbank extending across and blocking the mouth of a driveway or side road causes several problems. If the driver of a car or small truck attempts to traverse or drive through the snowbank in order to drive into or out of the intersecting road, then the vehicle may easily become “turtled”, i.e. the undercarriage of the vehicle becomes at least partially stuck and resting on the snowbank, such that the drive wheels no longer get sufficient traction to propel the vehicle farther forward. The vehicle is then stuck halfway in the driveway (or other intersecting road) and halfway in the plowed road, thereby creating a potential traffic hazard.
In order to keep the snowbank cleared from the mouth of the intersecting road, it will be necessary to perform additional snow removal work on the intersecting road every time the snowplow passes by along the main road. This requires the homeowner or the responsible plowing service to repeatedly plow the intersecting road every time the plow truck passes by along the main road. Alternatively, the homeowner must shovel away the snowbank by hand using a shovel whenever the plow truck passes along the main road. At best, this causes significant additional expense and effort for repeatedly clearing away the accumulated snowbank, or in the worst case causes health risks such as heart attacks. It has been recognized that shoveling dense hard snow, such as the compacted snow of a snowbank discharged from a snowplow, is a significant cause of heart attacks.
The above problems are exacerbated if the plow truck on the main road is also spreading road salt and gravel, or if the initial snowfall is wet and heavy. Such wet snow, or snow partially melted by road salt, will later freeze, thereby forming a hard crusty ridge or bank of ice extending continuously across the mouth of the driveway or other intersecting road. Such a frozen snowbank is extremely difficult to remove by plowing or hand tools, and may be impossible to remove with a snowblower or the like. The gravel and ice chunks present in such a snowbank easily damage or clog a snowblower. Also, after such a snowbank melts, the gravel remains on the driveway and causes an unsightly and unsafe condition, because vehicles and pedestrians may slip on the accumulated gravel.
Even if the snowbank in the mouth of the intersecting road is removed each time the plow passes by, the snowbank extending beyond the edges of the mouth of the intersecting road still becomes progressively higher with each plowing throughout the winter. The accumulated snowbank on both sides of the mouth of the intersecting road thus becomes a visual obstruction that blocks the view of the road by a driver exiting the intersecting road onto the main road.
For the above reasons, it is desired to be able to intermittently stop the discharge of snow from the discharge end of a snowplow as it passes by the mouth of a driveway or side road or other intersecting road that adjoins the main road being plowed. For convenience and efficiency, it is also desirable to achieve such an intermittent control of the snow discharge from the snowplow in an automatic manner.